Seam detector



May 2, 1967 J. w. WARD 3,316,760

SEAM DETECTOR Filed Nov. 9, 1964 v LU Lu /Q INVENTOR.

United States Patent Office 3,316,760 Patented May 2, 1967 3,316,760 SEAM DETECTOR John W. Ward, Charlottesville, Va., assignor, by mesne assignments, to Teledyne, Incorporated, Hawthorne,

Calif.

Filed Nov. 9, 1964, Ser. No. 409,649

Claims. (Cl. 73-159) This invention relates to devices for detecting seams in fabrics. Seam detectors have been marketed but they have not been satisfactory due to the fact that they have not reliably differentiated between seams and slubs. Prior detection devices have been placed on both edge areas of a travelling web or fabric, the idea being that a seam would actuate both devices more or less simultaneously, but a slub would actuate only one of the detectors. This was an improvement but still did not produce desired results since two aligned slubs would falsely indicate a seam.

My seam detector is designed to be sensitive to seams extending across the fabric, but not to slubs. A plurality of spaced rings are arranged to be kicked up by a seam to close electrical circuits almost simultaneously, i.e. within a given time interval. When this happens, the associated electrical or electromechanical indicating device such as a solenoid, meter, relay, lamp, or other device is connected in circuit to indicate a seam. Slubs, however, will not be indicated since it is highly unlikely that there would ever be enough slubs so positioned that all of the contacts would be closed within the given time interval.

A prior seam detector employs four or more freely rotatable rings any one of which, on encountering an increase in fabric thickness, makes contact with a stationary contact bar and closes a relay to cause external apparatus to function as though a seam were present. This external apparaus may be rollers, cutter knives, or other devices which should be actuated in the presence of a seam but not in the presence of a slub. Apparatus in use prior to my invention has attempted to eliminate the operation uncertainty by mounting two detector heads on opposite edges of the fabric. The first detector head sensing an increased thickness started a timing circuit and if the sec ond detector head sensed an increased fabric thickness during a predetermined time interval the detector system would indicate the presence of a seam even though no seam was present but only two separated slubs.

The fallacy of such prior systems has been in the long duration of the timed interval, which is essential if a skewed seam is to be detected. It is entirely possible for two slubs to appear, one on either edge area of the fabric, during the timed interval so that a false indication of a seam would be made. A typicaltiming interval might be set up to permit a skew of 6 inches. Each of the two seam detector heads would ordinarily cover the fabric for about 2 /2 inches. Therefore two slubs in 30 square inches of fabric are unidentifiable from a normal seam. In addition, prior systems require two sensing heads and the intermediate timing device and yet function as rather poor seam detectors. It is clear that there are both operational and economic disadvantages to prior seam detectors.

It is an object of my invention to provide a seam detector which will reliably differentiate between seams and slubs.

Another object is to provide a seam detector which can be built at reasonable cost.

A further object is to provide a seam detector which will allow for skewed seams and yet will differentiate between slubs and scams.

Another object is to provide a detector which will be responsive to thin seams.

Other objects will be evident in the following description.

In the drawings:

FIGURE 1 is a side elevation, in seam detector mechanism.

FIGURE 2 is a top plan view of the device shown in FIGURE 1.

FIGURE 3 is a circuit diagram of my seam detector electrical components.

In the mechanism shown in FIGURES l and 2 there are a plurality of rings 1 freely supported on rod 2 which is attached to arms 3 and 4 which are pivoted on long screw or rod 5 threaded into a hole in fixed support 6 which may be a part of the textile machine or any suitable support. Rings 1 may be of metal, plastic, or any suitable material. Plastic or other insulating bar 7 is attached to arms 3 and 4 and four sets of resilient contact members 8a and elements 9a; 8b, 9b; 8c, 9c; and 8d, 9d are attached to this bar, the contact elements and members being separated by insulating blocks 10. Adjustment screws 11 are threaded into block 7 and are adapted to adjust the separation of contact members 8a and ele ments 9a, etc., without touching elements 9a, etc. While a plurality of pairs of contact elements are shown it is obvious that metal rings may be used in conjunction with a plurality of fixed or adjustable contacts. The arms 3 and 4 are integral with or fastened to sleeve 12 which has bearing on rod 5.

The fabric 13 is moved underneath rings 1 and may be supported by plate 14. When a thickened portion of the moving fabric, such as a slub or seam, strikes one or more rings the struck rings are bounced upward to strike the associated contact element 9 and so to close momentarily the circuit including that contact element and the associated contact member 8. In the circuit diagram, FIG. 3, the common or ground conductor is shown at 15 and conductors 16, 17, 18, and 19, are connected to the respective associated contact elements 9a, 9b, 9c, 9d. Conductor 15 may be connected to the various contact members 8 or elements 9 may be connected to ground instead of members 8 if preferred.

Capacitors 20, 21, 22, and 23 connected as shown, are normally charged through conductor 24 and respective charging resistors 25, 26, 27, and 28 and common charging resistor 29. If a contact element associated with one of the capacitors 20, 21, 22, or 23 is deflected against its adjacent contact member, by one of the rings 1, then the associated capacitor is discharged and begins to recharge at a rate determined by the voltage on line 24, the resis tors in circuit, and the capacitance. If a plurality of rings close contacts at the same time, or nearly at the same time, the current which flows through resistor 29 is equivalent to substantially the sum of the individual charging cur-. rents for the capacitors involved. The magnitude of the current through resistor 29 is therefore indicative of the number of rings which have been deflectedupward to close associated contacts.

A typical charging time constant may be set up for milliseconds so that the peak total charging current exists for only about 30 milliseconds. By this arrangement, a seam is indicated only when a predetermined number of rings close associated contacts within 30 milliseconds. All other slub-caused contacts are ignored.

Since slub-caused contacts are ignored, mechanical clearance between the rings 1 and the contacts 8, 9, may be set to a minimum, thereby providing adequate sensitivity to detect thin seams.

In the circuit diagram the common charging current causes a voltage drop in resistor 29. This voltage drop is compared in a bridge comprising transistors Q3 and Q4, resistors 30 and 31, and potentiometer 32 to deterpart section, of my mine the magnitude of the charging current. When the present level is exceeded, transistor Q4 which was saturated, cuts off and transistor Q3 which was cut off, saturates. The resulting current pulse through diode 33 to the, collector of transistor Q3, initiates a one-shot multivibrator or similar circuit, shown in the dotted box, to cause energization of relay winding 34 to cause closing of relay contacts 35 and 36 and so to energize the output circuit including conductors 3'7 and 38 connected current source 39, and output device 40 which maybe a solenoid, a motor, a meter, or any suitable means for indicating a seam, for releasingpressure of the rolls, or otherwise.

In the circuit shown the one shot has a duration of 250 ms., which causes operation of relay 3445-66 which effects energization of output means 40 for seams only and not for slubs. The improvement in performance of my device, as compared to prior devices, becomes apparent by comparing the possibility of 2 slubs in 30 square inches in prior systems to 4 slubs in system. There is an increase of scam vs. slub discrimination of at least 20:1 in favor of my system. The use of a single seam detector head in my system reduces the cost of the apparatus and the simple electronics of the coincidence circuit offers considerable saving over relay timer devices of prior systems.

The values of components and various legends shown on the circuit diagram will make the circuit clearly understandable.

Due to the timing principle employed in my seam-detector system and to other characteristics such as the potential difference comparing circuits, I can set the sensitivity of my system to detect thin seams and maintain discrimination between such thin seams and small slubs, which has not been true of prior systems.

What I claim is:

1. In a seam detector, a plurality of electrical contact members, a plurality of mechanical seam-sensing elements a plurality of electrical contact elements for actuation by said seam-sensing elements to touch said electrical contact members, electrical circuit means in circuit with said 4 square inches for my contact elements and contact members, said circuit means including bridge means cooperating to provide a current proportional to the number of contacts closed within a pre-set time interval, and electrical output means actuated when a predetermined number of contacts are closed within said preset time interval.

2. In a seam detector, a plurality of electrical contact elements, a plurality of mechanical seam-sensing members for closing said contact elements due to passing of'a seam, electrical circuit means including a plurality of capacitances connected to be discharged when an associated contact element is actuated, an impedance in circuit with said capacitances, a bridge circuit for comparing the potential difference across said impedance with a preset value of potential difference, said electrical circuit means including a one-shot circuit for actuation by said connected bridge circuit when the compared potential difference exceeds a preset value within a predetermined interval of time, and relay means in circuit with said one-shot circuit for actuation thereby.

3. The seam detector as described in claim 2, and including impedance means for influencing the charging rate of said capacitances.

4. The method of detecting a seam in fabric, said method comprising discharging a plurality of capacitances as a result of passage of a seam, measuring the rate of re-charge of the discharged capacitances in terms of potential difference, comparing said potential difference with a preset potential difference, and using any difference between said potential differences to cause actuation of an electrical output circuit.

References Cited by the Examiner UNITED STATES PATENTS 2,636,951 4/1953 Fahringer 20061.13

LOUIS R. PRINCE, Primary Examiner.

W. A. HENRY, Assistant Examiner. 

1. IN A SEAM DETECTOR, A PLURALITY OF ELECTRICAL CONTACT MEMBERS, A PLURALITY OF MECHANICAL SEAM-SENSING ELEMENTS, A PLURALITY OF ELECTRICAL CONTACT ELEMENTS FOR ACTUATION BY SAID SEAM-SENSING ELEMENTS TO TOUCH SAID ELECTRICAL CONTACT MEMBERS, ELECTRICAL CIRCUIT MEANS IN CIRCUIT WITH SAID CONTACT ELEMENTS AND CONTACT MEMBERS, SAID CIRCUIT MEANS INCLUDING BRIDGE MEANS COOPERATING TO PROVIDE A CURRENT PROPORTIONAL TO THE NUMBER OF CONTACTS CLOSED WITHIN A PRE-SET TIME INTERVAL, AND ELECTRICAL OUTPUT MEANS ACTUATED WHEN A PREDETERMINED NUMBER OF CONTACTS ARE CLOSED WITHIN SAID PRESET TIME INTERVAL. 